The game takes place in the fantasy world of Radiata, where humans and fairy-like creatures known as "non-humans" coexist. The story follows Jack Russell, a 16-year-old knight who becomes embroiled in a conflict between humans and non-humans. A mysterious event known as the "Great Mutation" has caused many non-humans to turn against their human friends, and Jack must navigate this treacherous landscape to uncover the truth behind the mutation and restore peace to the land.